Based on my personal experience, I would not buy any MB other than 85 or earlier diesel models. My MB experience is with a 80 240D and an 87 300 SDL. I religiously tracked all failures in both cars. The 87 just had more failures, and they were all very expensive to repair. I have friends with newer model MBs, and I really believe quality and reliability have gone down.
I think we are all getting shafted by the auto industry, but I think we deserve it. If you look at the ads, and they are that way for a reason (they work), no one ever cares about reliability and longevity. It's all image BS.
Take the idiotic SUVs (stupid utility vechicles). They are prime examples of retro engineering...station wagons on pickup truck frames, with embarrassing fuel economies, handling characteristics of trucks, and stopping distances of a country mile. And they sell like crazy...why...because of image.
I think that collectively we are just too stupid to get a better deal.